LC-14 sign

Launch complex 14 is one of six launch sites in the Eastern
Test Range used to launch Atlas rockets, and the only
one used to launch humans. (The others were LC-11, LC-12, and
LC-13, all used to test variants of the SM-65 Atlas
nuclear missile; LC-36, used for space launch operations with
the Atlas II and Atlas III; and LC-41, used to
launch the Atlas V—there was never an Atlas
IV.)

Not mentioned on this sign are the unmanned
Mercury-Atlas 1 through 5, which were test flights.
Mercury-Atlas 1 failed during launch;
Mercury-Atlas 2, 3, and 4 were successful.
Mercury-Atlas 5 flew for two orbits with the chimpanzee
Enos, but problems with the spacecraft caused controllers to
terminate the mission early. Enos was recovered safely but died
a year later from an antibiotic-resistant infection. Shepard's
Mercury-Redstone mission took place between MA-3 and
MA-4; Grissom's flight took place between MA-4 and MA-5.